1. Field of the Invention
The present invention relates to a color cathode ray apparatus provided with an electron gun assembly of the in-line type and more particularly, a color cathode ray apparatus of the in-line type provided with a deflection unit.
2. Description of the Related Art
The color cathode ray apparatus of the in-line type has an envelope comprising a panel provided with a phosphor screen on which phosphor strips or dots for emitting three colors of red, green and blue are coated, a neck provided with an electron gun for emitting electron beams to the phosphor screen, and a funnel for connecting neck and the panel. The electron gun assembly of the in-line type for emitting three electron beams is housed in the neck. Arranged around the funnel are deflection magnetic fields generating unit for deflecting the electron beams in horizontal and vertical directions in such a manner that the phosphor screen is scanned with the electron beams emitted from the electron gun assembly. A shadow mask is so fixed to the panel as to face the phosphor screen and has a plurality of apertures, the electron beams passing through the aperture of the shadow mask and striking against the three-color phosphor strips or dots.
The deflection magnetic field generating units is so designed that horizontally deflecting magnetic field is of pin cushion shape, and that vertically deflecting magnetic field is of barrel shape. Thus, the three electron beams emitted from the electron gun assembly are converged upon the phosphor screen. This is called magnetic field of the self convergence type.
When the magnetic field is of the self convergence type like this, many advantages can be provided including that various kinds of terminals, convergence yokes and convergence circuit which are needed to adjust the convergence of beams are made unnecessary. However, the distortion of magnetic field is used to achieve the self convergence of beams, thereby causing the shape of electron beams to be distorted on the phosphor screen. FIG. 1A shows the spot shape of an electron beam deflected at an end region on the horizontal axis of the phosphor screen, said beam being distorted having bright core portion 22 longer in the horizontal direction and dark halo portion 23 longer in the vertical direction. FIG. 1B shows the spot shape of an electron beam deflected at an end region on the vertical axis of the phosphor screen, said beam being distorted having small and bright core portion 22 longer in the vertical direction and large and dark halo portion 23 longer in the vertical direction.
In the case of the color cathode ray apparatus of the in-line type, the spot shape of deflected beams is distorted, as described above, which causes the resolution of the color cathode ray tube to be deteriorated.